A ground fault circuit interrupter (GFCI), also called residual current device (RCD), is a device that shuts off an electric power circuit when it detects that a leakage (residual) current is flowing along an unintended path. The use of some protective devices is specifically required in the National Electrical Code (NEC), which defines a ground fault circuit interrupter as “a device intended for the protection of personnel that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds the values established for a Class A device.” A Class A GFCI trips when the current to ground has a value in the range of 4 milliamps to 6 milliamps.
Tripping characteristics of ground fault circuit interrupters can be described by a tripping curve plotting the amount of time required for the device to interrupt the electric circuit in dependency of a detected residual current level.
More specifically, on the one hand in standard UL 2231-2 “Personnel protection systems for electric vehicle (EV) supply circuits—Particular requirements for protection devices for use in charging systems for electric vehicle charging” UL as a standards developer in the US defines a tripping characteristic the protection devices need to be compliant with.
On the other the International Electrotechnical Commission (IEC) as a further international standards organization has prepared the standard IEC 62752:2016 “In-cable control and protection devices (IC-CPDs) for mode 2 charging of electric road vehicles”. This standard applies to portable devices performing simultaneously the functions of detection of the residual current, of comparison of the value of this current with the residual operating value and of opening of the protected circuit when the residual current exceeds this value.
Both standards are suggesting tripping characteristics for protection devices (GFCIs and RCDs) which are different from each other.
Consequently, the manufacturer of such protection devices are producing two different products each having its own tripping curve implemented: one product according to the UL standard and the other according to IEC standard.